Field of the Invention
The present invention relates to a belt driving roller including an electroviscous force developing member, and a belt driving device using the same.
Description of the Related Art
Generally, belt driving devices for driving and rotating an endless belt are configured to rotate the belt by rotating driving rollers by means of a tensile force between the driving rollers and a frictional force that are caused because the belt is tensed by the plurality of rollers over which the belt is hung by its internal surface (back surface).
According to this method, a belt skew, which is a shift of the belt toward an edge during its continuous rotation, occurs due to tensile force variations in the direction of the width of the belt. Hence, it is necessary to correct the belt skew by providing such a mechanism as described in Japanese Patent Application Laid-Open (JP-A) Nos. 2000-272772, 2000-198568, and 2000-147950. However, correction by means of swaying of a driven roller as described in JP-A No. 2000-198568 will be ineffective due to wear of the surface of this roller due to continuous use. Restriction of the belt skew by means of a guide member provided on the edge of the belt as described in JP-A No. 2000-147950 may cause the belt to be torn because a stress concentrates on a portion of the belt on which the guide member abuts.
Meanwhile, an electro-rheological gel (ER gel) that reversibly develops viscosity under an electric field has been reported (“Occurrence mechanism of shear stress in ER gel” (Collection of Papers by Japan Fluid Power System Society, vol. 36/no. 1, pp. 15-21 (January 2005))). According to this document, electro-rheological particles (ER particles) are dispersed in a silicone gel and exposed at the surface of the gel. It has been discovered that when an electric field is applied, the ER particles in the gel are attracted to each other, and the ER particles exposed at the surface are drawn into the gel, which upthrusts the gel and reversibly changes the surface condition. It is inferred that a relatively weak adhesive force on the surface due to a surface condition produced by the ER particles under no electric field changes to a greater adhesive force under an electric field due to the effect of the gel.
JP-A Nos. 2005-255701 and 2011-46785 describe use of an electro-rheological fluid in a power transmission device and a control device such as a clutch, a damper, a shock absorber, and a torque converter. U.S. Pat. No. 5,607,996 describes use of an electro-rheological elastomer composition that changes its Young's modulus by at least 2 Mpa upon application of an electric field in a transmission structure and a chassis structure of an automobile. The techniques of JP-A Nos. 2005-255701 and 2011-46785 intend to enhance the durability of the power transmission device and the control device such as the clutch, the damper, the shock absorber, and the torque converter in which the electro-rheological gel is used, by using a specific type of particles as the electro-rheological particles. The technique described in U.S. Pat. No. 5,607,996 relates to the electro-rheological elastomer composition obtained by dispersing the electro-rheological particles made of a polymerizable material in an elastomer material crude rubber, but does not relate to a belt.
Further, the present inventors have already proposed a powder transfer device including: a powder bearer, e.g., an image bearer; and a surface moving member movable synchronously with a surface moving speed of the powder bearer and having a surface capable of receiving a powder (e.g., a residual toner) from the surface of the powder bearer, wherein the surface moving member includes an electroviscous gel layer in which the electro-rheological particles that reversibly develop a viscosity force under an electric field are dispersed (JP-A No. 2012-42907).
As described above, the conventional technique described above drives the belt by imposing a tensile force between the plurality of rollers, which causes the belt skew and necessitates an additional mechanism for correcting the belt skew, which leads to a complicated device mechanism and durability limitation depending on the life span of the mechanism. The belt itself has also been required to have an enough strength and durability to endure a large tensile load constantly imposed thereon.